Development of an Odorant Co-­receptor Mutant Strain of the New World Screwworm Fly using the CRISPR/Cas9 system: A Functional Investigation on the Evolution of Olfactory Perception in Blowflies.

Abstract

Identifying genomic regions that underlie the adaptive radiation of insects is a major goal in modern evolutionary biology. The emergence of obligatory ectoparasitism in blowflies has been the subject for scientific debate for over a half-century, creating the need for studies regarding how genomic architecture is linked to adaptive ecological transitions. Previous studies suggested that this strategy arose twice within blowflies' lineage, presumable to avoid resource competition. However, the molecular bases underlying the transition of a free-living to an ectoparasitic habit in blowflies remain unknown. We hypothesize that olfaction might have played a critical role in this adaptation. To begin testing this, this project propose to functionally characterize the olfactory co-receptor Orco in the New World Screwworm fly (NWS), Cochiomyia hominivorax, by using the powerful genome editing CRISPR/Cas9 system to knockout this gene. Orco encodes a co-receptor that dimerizes with all Odorant-selective Receptors (ORs) and is required for the OR-perception pathway. After knocking the gene out in NWS, a stable Orco mutant strain will be developed, which functionally lacks the entire ORs family. This project focus on the establishment of the CRISPR system in NWS, but it will also provide important information about the odors associated with the ectoparasitism in blowflies by generating the first profile of responses mediated by olfactory receptors in C. hominivorax.